简介：Turbulencepropertiesofawall-boundedturbulentmixinglayerassociatedwithanopeningstepwereextensivelymeasuredusingI-andX-typehotwires.Theturbulentmixinglayerflowwasanalyzedintermsofwallstaticpressuredistribution,turbulenceintensity,Reynoldsstress,streamwisevelocityprofileandcontinuouswavelettransformcoefficients.Developmentofvorticalstructuresembeddedintheturbulentmixinglayerwastemporallyandspatiallyresolvedbyusingcontinuouswavelettransform.Theconstraintofthedownstreamsolidwallonthemixinglayerflowwasdelineated.

简介：Thecontrolofturbulencebydimples/pimpleshasdrawnmoreandmoreattention.Theobjectiveofthispaperistoinvestigatetheeffectivenessoftheactivedimples/pimplesforthedragreductionintheincompressibleturbulentflow.Firstly,thedragreductionbytheoppositioncontrolbasedonactivedimples/pimplesatthelowerwallisstudiedviathedirectnumericalsimulationoftheturbulentchannelflow.Itisfoundthatlargeactivedimples/pimplescannotsuppressthestreamwisevorticessignificantlyandthusalmostnodragreductionisachieved.Smallactivedimplesandpimpleswiththediameterofonefourthofthestreakwidthcanbothreducethefrictiondrag,butpimpleswillinducealargerpressuredragthandimples.Thenthesuboptimalcontrolschemeisexaminedbasedonsmallactivedimplesusingthespanwisewallshearinformationonly.Itisshownthatthefrictiondragdecreasesbyabout4.5%butthetotaldragisonlyreducedbyabout2.7%abatedbythepressuredrag.Comparedwiththeactuationoftheall-pointblowing/suctionortheall-pointwallmovement,theeffectivenessoftheturbulentdragreductionbasedonactiveshallowdimplesismuchsmaller.

简介：Anumericalsimulationisperformedforthermalinstabilityandheattransferofviscoelasticfluidsinboundedporousmediaunderthebottomconstantheatfluxboundarycondition.Theresultsforsixdifferentcombinationsofrelaxationandretardationtimesdemonstratetheexistenceofthethermalinstabilityinducedflowbifurcation.Itisfoundthattheincreaseoftherelaxationtimecanenhancetheheattransferefficiencybydisturbingthefluidflowandfacilitatingthebifurcation.Theincreaseoftheretardationtimecanstabilizetheflowandpostponethebifurcation,leadingtosimplerflowpatternandlowerheattransferrate.